Transcriptional termination in the Balbiani ring 1 gene is closely coupled to 3'-end formation and excision of the 3'-terminal intron

• Published in: Genes & development Vol. 12; no. 17; pp. 2759 - 2769
• Main Authors: Baurén, G, Belikov, S, Wieslander, L
• Format: Journal Article
• Language: English
• Published: United States Cold Spring Harbor Laboratory Press 01-09-1998
• Subjects: Animals; Chironomidae - genetics; Chironomidae - metabolism; Genes, Insect; Insect Proteins - biosynthesis; Insect Proteins - genetics; Introns; Medicin och hälsovetenskap; Polymerase Chain Reaction; Regulatory Sequences, Nucleic Acid; Research Paper; RNA Precursors - biosynthesis; RNA Precursors - genetics; Salivary Glands - metabolism; Sequence Deletion; Transcription, Genetic
• ISSN: 0890-9369; 1549-5477
• DOI: 10.1101/gad.12.17.2759

We have analyzed transcription termination, 3'-end formation, and excision of the 3'-terminal intron in vivo in the Balbiani ring 1 (BR1) gene and its pre-mRNA. We show that full-length RNA transcripts are evenly spaced on the gene from a position 300 bp upstream to a region 500-700 bp downstream of the polyadenylation sequence. Very few full-length transcripts and no short, cleaved, nascent transcripts could be observed downstream of this region. Pre-mRNA with 10-20 adenylate residues accumulates at the active gene and then rapidly leaves from the gene locus. Only polyadenylated pre-mRNAs could be detected in the nucleoplasm. Our results are consistent with the hypothesis that transcription termination occurs in a narrow region for the majority of transcripts, simultaneous with 3'-end formation. Excision of the 3'-terminal intron occurs before 3'-end formation in about 5% of the nascent transcripts. When transcription terminates, 3' cleavage takes place and 10-20 adenylate residues are added, the 3'-terminal intron is excised from additionally about 75% of the pre-mRNA at the gene locus. Our data support a close temporal and spatial coupling of transcription termination and the cleavage and initial polyadenylation of 3'-end formation. Excision of the 3'-terminal intron is highly stimulated as the cleavage/polyadenylation complex assembles and 3'-end formation is initiated.